Why does it throw Uncaught TypeError: Cannot read properties of undefined (reading 'split')?

Question

JavaScript

I made an extension, wrote the code:

let changeColor = document.getElementById('buttonBg');

if (changeColor != null) {
  changeColor.onclick = function(el) {  //ругается на эту строку.
    let colorBg = '#333';
    let colorText = '#fff'

    chrome.tabs.query({active: true, currentWindow: true}, function(tabs) {
      chrome.tabs.executeScript(
        tabs[0].id,
        {code: 'document.body.style.backgroundColor = "' + colorBg + '";document.body.style.color = "' + colorText + '"'}
      );
    })
  }
}

I include the code not in the html page, but in manifest.json, so I can't use onload and defer.

Answer 1

onload- can. Just not . True, this is not necessary, for it is indicated when to run it in the parameter . Similarly, not , but . In general, forget about when you climb on other people's pages. There can be only one such handler, while there can be as many as you like. Well, I don’t see anywhere in your code that the error is complaining about, so somewhere you are lying. onload addEventListener('load', ...)
split